In power electronics equipment, switching elements, such as silicon insulated gate bipolar transistors (IGBTs) and metal oxide semiconductor field effect transistors (MOSFETs), are used to switch between execution and stop of power supply for driving loads such as electric motors. Particularly in recent times, as next-generation switching devices having a high breakdown voltage and a low loss, MOSFETs including silicon carbide (SiC) receive attention.
As a power semiconductor device, a vertical MOSFET structure is often used. The vertical MOSFET includes a planar type, a trench (trench-gate) type, or the like depending on its gate structure.
When a trench-gate SiC-MOSFET is formed on a substrate having an off-angle, such as 4° off, it has been known that an on-current and a threshold voltage are changed depending on sidewall surfaces of a trench being formed (for example, Patent Document 1).